There is a substantial prevalence of exposure to smoking and alcohol cues in movies and advertising viewed by adolescents, and these exposures have been indicated as an influence on adolescent smoking and alcohol use. However, there has been little research on factors that moderate the impact of media exposures. Our preliminary data provide evidence that good self-control reduces the impact of media exposures on adolescent smoking and alcohol use, but the scope and mechanism of this effect is not well understood. The proposed research to clarify the nature and mechanisms of moderation will be conducted by a multidisciplinary group of investigators who have been collaborating in studying media effects. The research design incorporates both field research and laboratory studies. The field study will examine the nature of moderation effects in an epidemiologic design with a sample of 1,800 younger adolescents followed over a 4-year period, while four laboratory studies with samples of 120 adolescents and young adults in 3 sites will examine specific hypotheses about the mechanism of moderation effects in controlled research with explicit and implicit cognitive measures. The research is based on a dual-process theoretical model which hypothesizes that good self-control will have a protective moderation effect for onset and/or progression of smoking and alcohol use whereas poor regulation will have a vulnerability effect. This will be investigated in the field study through testing how pathways from media exposure to expectancies, peer affiliations, and smoking/drinking behavior differ for self-control subgroups. The laboratory studies are designed to investigate four hypothesized mechanisms of moderation through studying effects of self- control constructs on encoding of information and enactment of proximal influences for substance use. We hypothesize that moderation may occur through differential encoding of risk and reward cues in media presentations; differential reactions to seeing smokers and drinkers in media; differential memory accessibility of expectancies about smoking and alcohol use; or differences in social competence and resistance efficacy in peer situations where there is pressure for smoking or drinking. The combination of field and laboratory studies will provide more detailed knowledge about media effects on adolescent smoking and alcohol use than can be obtained from either design conducted alone. The proposed research has theoretical significance because it provides an opportunity to obtain new knowledge about a moderation effect that has not been extensively studied. Findings from the research will be useful for informing media literacy programs by showing more about the processes through which adolescents interact with media presentations and suggesting strategies for designing health communications for more or less vulnerable groups. Thus the research program will have implications for both basic research on media influence and for media-oriented prevention research on smoking/alcohol use.